Genshi templates use dgettext to reliably extract and translate special
content like button labels. Because for the 0.11 Trac releases this isn't
included into default content of the data object passed to Genshi alongside
with the template, this has to be added explicitely to each and every data
object created with this plugin.

More importantly, there is some code missing to degrade more complex i18n
calls like dgettext gracefully for Trac 0.11, so more code has been taken
and adapted from current Trac trunk to fill in the gap here.

Fixes #9008: If the referenced ticket didn't have a change log (at least 1 ticket comment), the ticket's cnum would not be correctly set to 1 and an exception would result. This defect appears to have been introduced in [9658].

Similar to root=, if you specify a "goal", the chart shows all the
tickets required for the specified goal. Follows the configurd 'pred'
field.

goal=self in a ticket description or comment displays the current
tickets predecessors.

root, goal, and id all add to the list of tickets to display but
do *not* interact. If you specify root=1,goal=2, you get the
descendants of 1 and predecessors of 2 but not the descendants of the
predecessors or 2.